Desktop and notebook computers running in enterprises and residential settings consume a significant amount of energy even when they are idle. Studies have shown that idle power consumption may be up to approximately 40% of a computer's peak power demands. Turning desktop or notebook computers off or putting them into deep sleep/hibernation modes may eliminate this consumption. However, desktop and notebook computers typically run a number of applications with always-on semantics, many of them requiring persistent network presence, such as VoIP, IM, email, personal media sharing, etc. Turning the computers off or putting them in sleep mode affects the usability of the desktop or notebook computers by preventing them from participating in background activity, such as network resource discovery, operating system (OS) and software updates, peer-to-peer file-sharing, and remote access. Further, there are commonly instances in which desktop computers experience periods of brief idleness interspersed with active use.